It's a very basic and fundamental word, and it's found in many languages, often with slight variations in spelling but the same meaning.
For example, in English, we have:
* Duet: A musical piece performed by two people.
* Duopoly: A market dominated by two companies.
* Dual: Having two parts or aspects.
So, next time you see "duo" in a word, you can remember that it's just a fancy way of saying "two"!